Superfinishing and grinding machines for crankshifts, camshifts and the like articles are known to enable the abrasive finishing of the running surfaces of such workpieces utilizing an action which combines rotation of the workpiece and a linear reciprocation thereof in the axial direction.
To this end conventional machines for this purpose can comprise a chuck or other device for securing the workpiece at one end to a spindle, means for rotating the spindle and an oscillating drive for imparting the axial reciprocation to the workpiece. A tool holder generally is provided with a number of stones which engage the workpiece as the tools for effecting the finishing operation.
The chuck spindle can be mounted in a spindle stock or head and generally means can be provided, not only for axially reciprocating the spidnle shaft, but also for setting the axial stroke of the spindle shaft necessary for receiving and removing the workpiece.
The spindle sleeve can cooperate with a stirrup-shaped member to effect the oscillating drive in the axial direction.
The spindle stock (headstock) is generally a slide which is guided on a track or bed and also carries the oscillating drive. The slide can generally be displaced for the aforementioned clamping stroke or setting stroke. The mechanism for the setting stroke does not operate directly upon the spindle shaft, therefore, but rather acts upon the slide. During the setting stroke, the oscillating drive is entrained as well.
The slide can generally also be raisable and lowerable for receiving the workpiece.
When the fabrication tolerances are extremely narrow and great precision in finishing the workpiece is desired, the conventional grinding machine of the aforedescribed type is frequently unsatisfactory because its precision is insufficient.
Part of the problem is the fact that there are two distinct tolerances which have to be taken into consideration, namely, the guide tolerances of the oscillatingly movable spindle shaft during the oscillating operation and the guide tolerances of the spindle stock sliding in its guide. Because these tolerances are statically additive, this system is largely unsatisfactory.